unit 4: plant disease management for field crops
TRANSCRIPT
Unit 4: Plant Disease Unit 4: Plant Disease Management for Field Management for Field
CropsCrops
Unit 4: Plant Disease Unit 4: Plant Disease Management for Field Management for Field
CropsCrops Unit 4 Objectives:Unit 4 Objectives:
– Discuss some common plant disease Discuss some common plant disease problems of common field crops in ILproblems of common field crops in IL
– Awareness of possible Awareness of possible prevention/treatment methodsprevention/treatment methods
– Understanding of the types of chemicals Understanding of the types of chemicals or treatments necessary for controlor treatments necessary for control
Unit 4: Plant Disease Unit 4: Plant Disease Management for Field Management for Field
CropsCrops Crop yield and quality is affected by Crop yield and quality is affected by
disease each year in ILdisease each year in IL Disease management strategies Disease management strategies
should be part of your IPM planshould be part of your IPM plan– Resistant or tolerant varieties of cropResistant or tolerant varieties of crop– Crop rotationsCrop rotations– FungicidesFungicides
Use in conjunction w/ other practices or as a Use in conjunction w/ other practices or as a last resortlast resort
– Appropriate agronomic practicesAppropriate agronomic practices
Unit 4: Plant Disease Unit 4: Plant Disease Management for Field Management for Field
CropsCrops Success often depends on amount of Success often depends on amount of
scouting, stage of identification, and scouting, stage of identification, and accuracy of diagnosisaccuracy of diagnosis– Proper scouting will ensure that Proper scouting will ensure that
controls/treatments are used at the controls/treatments are used at the most effective timesmost effective times
– Can help prevent an economic lossCan help prevent an economic loss
Unit 4: Plant Disease Unit 4: Plant Disease Management for Field Management for Field
CropsCrops Disease DiagnosisDisease Diagnosis
– Accurate diagnosis is critical first step for Accurate diagnosis is critical first step for controlcontrol
– Many diseases or nutrient deficiencies Many diseases or nutrient deficiencies can cause the same symptomscan cause the same symptoms
– Must correctly diagnose in order to Must correctly diagnose in order to prevent unnecessary applicationsprevent unnecessary applications
– Plants should be collected for Plants should be collected for identification as soon as disease is identification as soon as disease is suspectedsuspected Is this always realistic?Is this always realistic?
Unit 4: Plant Disease Unit 4: Plant Disease Management for Field Management for Field
CropsCrops– Best to try to identify the disease while Best to try to identify the disease while
the plant is still alivethe plant is still alive– Samples can either be sent to the Plant Samples can either be sent to the Plant
Clinic at U of I or be taken to the local Clinic at U of I or be taken to the local Extension OfficeExtension Office
Read the LabelRead the Label– Make sure you understand all Make sure you understand all
restrictions associated w/ each chemicalrestrictions associated w/ each chemical– These chemicals may not be used as These chemicals may not be used as
frequently as herbicides or insecticides, frequently as herbicides or insecticides, so you may not be as up to date w/ so you may not be as up to date w/ themthem
Unit 4: Plant Disease Unit 4: Plant Disease Management for Field Management for Field
CropsCrops– Must be purchased and applied by a Must be purchased and applied by a
licensed applicatorlicensed applicator Fungicide GuidelinesFungicide Guidelines
– Seed TreatmentsSeed Treatments Greatest benefits found when:Greatest benefits found when:
– Seed is low quality due to damage or fungal Seed is low quality due to damage or fungal infestationinfestation
– Seedbed is cool and wet delaying germination Seedbed is cool and wet delaying germination and emergenceand emergence
– Low seeding ratesLow seeding rates Should not be used as a substitute for good Should not be used as a substitute for good
quality seedquality seed
Unit 4: Plant Disease Unit 4: Plant Disease Management for Field Management for Field
CropsCrops Low yields and economic losses will still be Low yields and economic losses will still be
realized w/ low quality or damaged seedrealized w/ low quality or damaged seed Selection is crucialSelection is crucial
– Some treatments may only control specific Some treatments may only control specific pathogenspathogens
– Foliar TreatmentsFoliar Treatments May reduce losses in corn, soybeans, and May reduce losses in corn, soybeans, and
small grainssmall grains Should only be used on fields w/ an expected Should only be used on fields w/ an expected
disease severitydisease severity If the disease is diagnosed early, and If the disease is diagnosed early, and
fungicide applied correctly, should have fungicide applied correctly, should have maximum benefitmaximum benefit
Unit 4: Plant Disease Unit 4: Plant Disease Management for Field Management for Field
CropsCrops Fungicides applied to corn usually reserved Fungicides applied to corn usually reserved
for seed-production fieldsfor seed-production fields– Leaf blightsLeaf blights– Gray leaf spotGray leaf spot– Rust diseasesRust diseases– Generally justified only when disease is prevalent Generally justified only when disease is prevalent
within 1-2 weeks of tasselingwithin 1-2 weeks of tasseling– Infections occurring 1-2 weeks or later after Infections occurring 1-2 weeks or later after
tasseling usually not economically controlledtasseling usually not economically controlled
Foliar fungicides applied to small grainsFoliar fungicides applied to small grains– RustsRusts– SeptoriaSeptoria
Unit 4: Plant Disease Unit 4: Plant Disease Management for Field Management for Field
CropsCrops– Leaf blightsLeaf blights– Tan spotTan spot– These tend to occur after inadequate rotations These tend to occur after inadequate rotations
and during damp weatherand during damp weather Most damage occurs from emergence to flag Most damage occurs from emergence to flag
leaf/early milk stageleaf/early milk stage– Fungicides can increase yields, seed weight, and Fungicides can increase yields, seed weight, and
qualityquality– Decisions to spray should be based on the Decisions to spray should be based on the
amount of disease at flag leaf emergenceamount of disease at flag leaf emergence
Use of adjuvants is recommended Use of adjuvants is recommended (especially for corn and small grains)(especially for corn and small grains)
Unit 4: Plant Disease Unit 4: Plant Disease Management for Field Management for Field
CropsCrops Nematicide ApplicationsNematicide Applications
– Granular forms for corn and sorghum Granular forms for corn and sorghum should be applied as band treatmentsshould be applied as band treatments
– Should only be used when soil analysis Should only be used when soil analysis shows high numbers of parasitic shows high numbers of parasitic nematodesnematodes
– Not designed to replace crop rotation or Not designed to replace crop rotation or use of resistant varietiesuse of resistant varieties
Unit 4: Plant Disease Unit 4: Plant Disease Management for Field Management for Field
CropsCrops Alfalfa Seedling BlightAlfalfa Seedling Blight
– Caused by soil-borne fungiCaused by soil-borne fungi– Often occurs under wet conditionsOften occurs under wet conditions– Usually the first disease stress alfalfa Usually the first disease stress alfalfa
may encountermay encounter– Often leads to poor or stunted standsOften leads to poor or stunted stands
May survive, but yields will be reducedMay survive, but yields will be reduced
Unit 4: Plant Disease Unit 4: Plant Disease Management for Field Management for Field
CropsCrops– Easy way to suspect is if alfalfa stand Easy way to suspect is if alfalfa stand
emerges, but weeds grow quickeremerges, but weeds grow quicker Alfalfa usually grows very aggressively and Alfalfa usually grows very aggressively and
crowds out weedscrowds out weeds
Unit 4: Plant Disease Unit 4: Plant Disease Management for Field Management for Field
CropsCrops Alfalfa Root rotsAlfalfa Root rots
– Phytophthora, Fusarium wilt, Phytophthora, Fusarium wilt, AphanomycesAphanomyces
– Causes poor seedling stands, as well as, Causes poor seedling stands, as well as, root damageroot damage
– Identified by lesions on the taproot, Identified by lesions on the taproot, subsequent disintegration of root tissue, subsequent disintegration of root tissue, and deathand death
– Control w/ resistant varietiesControl w/ resistant varieties
Unit 4: Plant Disease Unit 4: Plant Disease Management for Field Management for Field
CropsCrops Corn Gray Leaf SpotCorn Gray Leaf Spot
– Early symptoms are signified by 1/16” olive Early symptoms are signified by 1/16” olive spots on the leaves w/ a yellow halospots on the leaves w/ a yellow halo
– At two weeks the spots are their signature gray At two weeks the spots are their signature gray or tan coloror tan color ¾ to 2 ½” long¾ to 2 ½” long Run parallel to leaf veinsRun parallel to leaf veins Begins on lower leaves and can spread upwardBegins on lower leaves and can spread upward Entire leaf may appear gray under extreme Entire leaf may appear gray under extreme
conditionsconditions
– Moist conditions and 70-85 degrees are idealMoist conditions and 70-85 degrees are ideal
Unit 4: Plant Disease Unit 4: Plant Disease Management for Field Management for Field
CropsCrops Corn Stalk RotCorn Stalk Rot
– FusariumFusarium Leaves turn from healthy green to dull greenLeaves turn from healthy green to dull green Lower stalk yellowsLower stalk yellows Stalk easily collapses and will cause lodgingStalk easily collapses and will cause lodging Inside of the stalk may be pinkInside of the stalk may be pink Favorable conditionsFavorable conditions
– Dry earlyDry early– Above avg. rain midseasonAbove avg. rain midseason– Temps 80-100 degreesTemps 80-100 degrees
– Many other types of stalk rot are knownMany other types of stalk rot are known
Unit 4: Plant Disease Unit 4: Plant Disease Management for Field Management for Field
CropsCrops Soybean Brown Stem RotSoybean Brown Stem Rot
– Soil borne disease that becomes visible Soil borne disease that becomes visible late in the seasonlate in the season
– Survives on plant material that may be Survives on plant material that may be buried >1’ deepburied >1’ deep Infects the roots and stem early in lifeInfects the roots and stem early in life Grows w/ the plantGrows w/ the plant Often infects the xylem tissue and restricts Often infects the xylem tissue and restricts
nutrient and water passage as the plant nutrient and water passage as the plant maturesmatures
Unit 4: Plant Disease Unit 4: Plant Disease Management for Field Management for Field
CropsCrops– SymptomsSymptoms
Typically not visible until late reproductive Typically not visible until late reproductive stagesstages
May not be visible at allMay not be visible at all Internal browning of vascular tissue in stem Internal browning of vascular tissue in stem
and/or leavesand/or leaves Leaves may have appearance similar to high Leaves may have appearance similar to high
temperature scorchingtemperature scorching May occur in circular patternsMay occur in circular patterns
– Favorable weather conditionsFavorable weather conditions Cool wet conditions either in early Cool wet conditions either in early
development or at reproductive stagesdevelopment or at reproductive stages Development inhibited above 80ºDevelopment inhibited above 80º
Unit 4: Plant Disease Unit 4: Plant Disease Management for Field Management for Field
CropsCrops Soybean Phytophthora Root RotSoybean Phytophthora Root Rot
– Spores reside in the soilSpores reside in the soil Germinate under wet conditions to form Germinate under wet conditions to form
more sporesmore spores Mobile w/ soil waterMobile w/ soil water Encysts on soybean rootsEncysts on soybean roots
– SymptomsSymptoms Stand reduction either pre or Stand reduction either pre or
postemergencepostemergence Leaves may wiltLeaves may wilt Water soaked lesions on stem and/or rootsWater soaked lesions on stem and/or roots
Unit 4: Plant Disease Unit 4: Plant Disease Management for Field Management for Field
CropsCrops– Favorable ConditionsFavorable Conditions
>60º temps>60º temps Very wet soilsVery wet soils
– Poorly drainedPoorly drained– Low areasLow areas– Compacted soilsCompacted soils– High clay soilsHigh clay soils– Not restricted to these areas onlyNot restricted to these areas only
Unit 4: Plant Disease Unit 4: Plant Disease Management for Field Management for Field
CropsCrops Soybean Cyst NematodeSoybean Cyst Nematode
– Very similar symptoms to many other Very similar symptoms to many other diseasesdiseases Can go undetected as the cause of economic Can go undetected as the cause of economic
loss for many yearsloss for many years
– Will often occur in circular/oval shaped Will often occur in circular/oval shaped patternspatterns Infected plants will be less vigorous and Infected plants will be less vigorous and
somewhat yellowsomewhat yellow May be slow to fill foliageMay be slow to fill foliage
Unit 4: Plant Disease Unit 4: Plant Disease Management for Field Management for Field
CropsCrops– Severity of symptoms can vary greatly Severity of symptoms can vary greatly
from nonexistent to very visiblefrom nonexistent to very visible– Infections cause dwarfed and stunted root Infections cause dwarfed and stunted root
systemssystems Can reduce the number of nitrogen-fixing Can reduce the number of nitrogen-fixing
nodesnodes Roots may be susceptible to other diseasesRoots may be susceptible to other diseases
– True identification can only be done by True identification can only be done by root examinationroot examination White/yellow oval shaped eggs on the rootsWhite/yellow oval shaped eggs on the roots Nodes are much smaller than the nitrogen Nodes are much smaller than the nitrogen
nodesnodes
Unit 4: Plant Disease Unit 4: Plant Disease Management for Field Management for Field
CropsCrops Asian Soybean RustAsian Soybean Rust
– Severe foliar damageSevere foliar damage Destroys photosynthetic tissueDestroys photosynthetic tissue Early defoliationEarly defoliation Early maturationEarly maturation
– Yield losses can be 10-80%Yield losses can be 10-80%– 6 hours of wet conditions and temps 59-6 hours of wet conditions and temps 59-
82º ideal for germination82º ideal for germination Dry conditions will restrict itDry conditions will restrict it
Unit 4: Plant Disease Unit 4: Plant Disease Management for Field Management for Field
CropsCrops– Spores penetrate cells directly instead Spores penetrate cells directly instead
of wait for another opening in the leafof wait for another opening in the leaf 9-10d from initial infection to next stage of 9-10d from initial infection to next stage of
spore productionspore production
– Common hosts include kudzu, vetch, Common hosts include kudzu, vetch, yellow sweet cloveryellow sweet clover
– Spreads w/ wind patternsSpreads w/ wind patterns
Unit 4: Plant Disease Unit 4: Plant Disease Management for Field Management for Field
CropsCrops Wheat Septoria Leaf BlotchWheat Septoria Leaf Blotch
– Recognized by oval shaped lesions on Recognized by oval shaped lesions on the leavesthe leaves Centers of the lesions may be grayishCenters of the lesions may be grayish May ooze when squeezed under high May ooze when squeezed under high
humidity conditionshumidity conditions
– Spores only mobile by splashing Spores only mobile by splashing raindropsraindrops
– Also infect stems and headAlso infect stems and head Head become purple-streakedHead become purple-streaked
Unit 4: Plant Disease Unit 4: Plant Disease Management for Field Management for Field
CropsCrops– Can result in low test weight and Can result in low test weight and
shriveled seedsshriveled seeds– Usually survives on straw and inoculates Usually survives on straw and inoculates
the following crop yearthe following crop year– Favorable conditions:Favorable conditions:
Splashing rainsSplashing rains Temps between 68-82ºTemps between 68-82º
Unit 4: Plant Disease Unit 4: Plant Disease Management for Field Management for Field
CropsCrops Wheat Fusarium Head Blight (Scab)Wheat Fusarium Head Blight (Scab)
– Caused reduced yield and grain qualityCaused reduced yield and grain quality– May also contaminate grain w/ mycotoxinsMay also contaminate grain w/ mycotoxins
Vomitoxin – not extremely toxic when fed, but Vomitoxin – not extremely toxic when fed, but will decrease consumption and feed efficiency will decrease consumption and feed efficiency (non ruminants most sensitive)(non ruminants most sensitive)
– Favorable conditions:Favorable conditions: Humid during floweringHumid during flowering
– Identified by bleached spikelets of the Identified by bleached spikelets of the headhead May even kill the developing seed in the dough May even kill the developing seed in the dough
stagestage
Unit 4: Plant Disease Unit 4: Plant Disease Management for Field Management for Field
CropsCrops Unit 4 Assignment:Unit 4 Assignment:
– Create a treatment protocol for each of Create a treatment protocol for each of the discussed diseasesthe discussed diseases Product and active ingredientProduct and active ingredient Application rateApplication rate Application methodsApplication methods Time of applicationTime of application
– Bring an article on a plant diseaseBring an article on a plant disease One page written summaryOne page written summary
– 20 points -- Due next time!20 points -- Due next time!